LXR linux/fs/iomap/swapfile.c

   1// SPDX-License-Identifier: GPL-2.0
   2/*
   3 * Copyright (C) 2018 Oracle.  All Rights Reserved.
   4 * Author: Darrick J. Wong <darrick.wong@oracle.com>
   5 */
   6#include <linux/module.h>
   7#include <linux/compiler.h>
   8#include <linux/fs.h>
   9#include <linux/iomap.h>
  10#include <linux/swap.h>
  11
  12/* Swapfile activation */
  13
  14struct iomap_swapfile_info {
  15        struct iomap iomap;             /* accumulated iomap */
  16        struct swap_info_struct *sis;
  17        uint64_t lowest_ppage;          /* lowest physical addr seen (pages) */
  18        uint64_t highest_ppage;         /* highest physical addr seen (pages) */
  19        unsigned long nr_pages;         /* number of pages collected */
  20        int nr_extents;                 /* extent count */
  21        struct file *file;
  22};
  23
  24/*
  25 * Collect physical extents for this swap file.  Physical extents reported to
  26 * the swap code must be trimmed to align to a page boundary.  The logical
  27 * offset within the file is irrelevant since the swapfile code maps logical
  28 * page numbers of the swap device to the physical page-aligned extents.
  29 */
  30static int iomap_swapfile_add_extent(struct iomap_swapfile_info *isi)
  31{
  32        struct iomap *iomap = &isi->iomap;
  33        unsigned long nr_pages;
  34        uint64_t first_ppage;
  35        uint64_t first_ppage_reported;
  36        uint64_t next_ppage;
  37        int error;
  38
  39        /*
  40         * Round the start up and the end down so that the physical
  41         * extent aligns to a page boundary.
  42         */
  43        first_ppage = ALIGN(iomap->addr, PAGE_SIZE) >> PAGE_SHIFT;
  44        next_ppage = ALIGN_DOWN(iomap->addr + iomap->length, PAGE_SIZE) >>
  45                        PAGE_SHIFT;
  46
  47        /* Skip too-short physical extents. */
  48        if (first_ppage >= next_ppage)
  49                return 0;
  50        nr_pages = next_ppage - first_ppage;
  51
  52        /*
  53         * Calculate how much swap space we're adding; the first page contains
  54         * the swap header and doesn't count.  The mm still wants that first
  55         * page fed to add_swap_extent, however.
  56         */
  57        first_ppage_reported = first_ppage;
  58        if (iomap->offset == 0)
  59                first_ppage_reported++;
  60        if (isi->lowest_ppage > first_ppage_reported)
  61                isi->lowest_ppage = first_ppage_reported;
  62        if (isi->highest_ppage < (next_ppage - 1))
  63                isi->highest_ppage = next_ppage - 1;
  64
  65        /* Add extent, set up for the next call. */
  66        error = add_swap_extent(isi->sis, isi->nr_pages, nr_pages, first_ppage);
  67        if (error < 0)
  68                return error;
  69        isi->nr_extents += error;
  70        isi->nr_pages += nr_pages;
  71        return 0;
  72}
  73
  74static int iomap_swapfile_fail(struct iomap_swapfile_info *isi, const char *str)
  75{
  76        char *buf, *p = ERR_PTR(-ENOMEM);
  77
  78        buf = kmalloc(PATH_MAX, GFP_KERNEL);
  79        if (buf)
  80                p = file_path(isi->file, buf, PATH_MAX);
  81        pr_err("swapon: file %s %s\n", IS_ERR(p) ? "<unknown>" : p, str);
  82        kfree(buf);
  83        return -EINVAL;
  84}
  85
  86/*
  87 * Accumulate iomaps for this swap file.  We have to accumulate iomaps because
  88 * swap only cares about contiguous page-aligned physical extents and makes no
  89 * distinction between written and unwritten extents.
  90 */
  91static loff_t iomap_swapfile_activate_actor(struct inode *inode, loff_t pos,
  92                loff_t count, void *data, struct iomap *iomap,
  93                struct iomap *srcmap)
  94{
  95        struct iomap_swapfile_info *isi = data;
  96        int error;
  97
  98        switch (iomap->type) {
  99        case IOMAP_MAPPED:
 100        case IOMAP_UNWRITTEN:
 101                /* Only real or unwritten extents. */
 102                break;
 103        case IOMAP_INLINE:
 104                /* No inline data. */
 105                return iomap_swapfile_fail(isi, "is inline");
 106        default:
 107                return iomap_swapfile_fail(isi, "has unallocated extents");
 108        }
 109
 110        /* No uncommitted metadata or shared blocks. */
 111        if (iomap->flags & IOMAP_F_DIRTY)
 112                return iomap_swapfile_fail(isi, "is not committed");
 113        if (iomap->flags & IOMAP_F_SHARED)
 114                return iomap_swapfile_fail(isi, "has shared extents");
 115
 116        /* Only one bdev per swap file. */
 117        if (iomap->bdev != isi->sis->bdev)
 118                return iomap_swapfile_fail(isi, "outside the main device");
 119
 120        if (isi->iomap.length == 0) {
 121                /* No accumulated extent, so just store it. */
 122                memcpy(&isi->iomap, iomap, sizeof(isi->iomap));
 123        } else if (isi->iomap.addr + isi->iomap.length == iomap->addr) {
 124                /* Append this to the accumulated extent. */
 125                isi->iomap.length += iomap->length;
 126        } else {
 127                /* Otherwise, add the retained iomap and store this one. */
 128                error = iomap_swapfile_add_extent(isi);
 129                if (error)
 130                        return error;
 131                memcpy(&isi->iomap, iomap, sizeof(isi->iomap));
 132        }
 133        return count;
 134}
 135
 136/*
 137 * Iterate a swap file's iomaps to construct physical extents that can be
 138 * passed to the swapfile subsystem.
 139 */
 140int iomap_swapfile_activate(struct swap_info_struct *sis,
 141                struct file *swap_file, sector_t *pagespan,
 142                const struct iomap_ops *ops)
 143{
 144        struct iomap_swapfile_info isi = {
 145                .sis = sis,
 146                .lowest_ppage = (sector_t)-1ULL,
 147                .file = swap_file,
 148        };
 149        struct address_space *mapping = swap_file->f_mapping;
 150        struct inode *inode = mapping->host;
 151        loff_t pos = 0;
 152        loff_t len = ALIGN_DOWN(i_size_read(inode), PAGE_SIZE);
 153        loff_t ret;
 154
 155        /*
 156         * Persist all file mapping metadata so that we won't have any
 157         * IOMAP_F_DIRTY iomaps.
 158         */
 159        ret = vfs_fsync(swap_file, 1);
 160        if (ret)
 161                return ret;
 162
 163        while (len > 0) {
 164                ret = iomap_apply(inode, pos, len, IOMAP_REPORT,
 165                                ops, &isi, iomap_swapfile_activate_actor);
 166                if (ret <= 0)
 167                        return ret;
 168
 169                pos += ret;
 170                len -= ret;
 171        }
 172
 173        if (isi.iomap.length) {
 174                ret = iomap_swapfile_add_extent(&isi);
 175                if (ret)
 176                        return ret;
 177        }
 178
 179        /*
 180         * If this swapfile doesn't contain even a single page-aligned
 181         * contiguous range of blocks, reject this useless swapfile to
 182         * prevent confusion later on.
 183         */
 184        if (isi.nr_pages == 0) {
 185                pr_warn("swapon: Cannot find a single usable page in file.\n");
 186                return -EINVAL;
 187        }
 188
 189        *pagespan = 1 + isi.highest_ppage - isi.lowest_ppage;
 190        sis->max = isi.nr_pages;
 191        sis->pages = isi.nr_pages - 1;
 192        sis->highest_bit = isi.nr_pages - 1;
 193        return isi.nr_extents;
 194}
 195EXPORT_SYMBOL_GPL(iomap_swapfile_activate);
 196